Many poor people can probably buy food cheaper than he can, so perhaps he's aiming for an especially low budget. In any case, he may have trouble getting all the nutrients he needs.

So I created a diet for him with Wagmu. I found a diet that costs about $1.39. This cost is only a guesstimate, because it depends on where the supplies are bought, and whether they are bought in bulk, taxes, etc. Here's the diet:

Not too thrilling! But the nutrient profile looks okay - 100% of everything:

Caveats on this diet:
(1) It's designed for only 1,400 calories. I'm dieting at the moment, and that's what Wagmu is giving me. I bet many poor people often get less than that. But given Mr. Affleck's build and active lifestyle, he will feel hungry with this diet.
(2) I didn't put in all the amino acids. Still one of those things I have to get around to doing, to upgrade Wagmu.
(3) Normal legal disclaimer, see your doctor first, this is only for entertainment purposes, use at your own risk, your mileage may vary, etc.

But is this fair to the poor people? They don't have access to state-of-the-art decision support for diet. They'll be eating whatever they can get, which is unlikely to be nearly as nutritious as the food plan above. So maybe Mr. Affleck should be left to fend for himself, rather than use this carefully designed plan. On the other hand, maybe the above diet really would convey what poor people have to eat, given its lack of palatability.